Mechanical seal failure

We are facing multiple seal failures (NDE side seal) in one of our multistage NGL pump . When opened the seal we found water, some black paste, one of the shaft O ring disintegrated, other O rings elongated  etc after only 6 month in service. The seal is from  Flexibox with API plan 53C . The O ring is Viton and supplied by OEM.  The symptoms begins with loosing the barrier seal which required frequent top up.

We suspect   pump product is entering inside seal due to O ring issue and causing spring hangup . Another doubt is assembly error during seal refurbishment. But as per the maintenance who refurbish the seal ( Replacing all parts except casing with new spares) there is no chance for any fitting error as it is a cartridge type seal and passes  the static test every time.

My question is how can we test the O ring in a practical way whether it is compatible for this service. Please bear in mind DE side also uses same components.

Is there any way the product can come to seal other than through secondery seals as the barrier pressure is always high

Is there any error during seal assembly is possible and if yes please explain

Any other thoughts are welcome

 

Original Post

https://www.marcorubber.com/o-ring-failure.htm

https://www.prepol.com/solutio...o-ring-failure-modes

http://www.dichtomatik.mx/cata...alisis-de-fallas.pdf

http://www.pspglobal.com/seal-failure.html

http://www.madgetech.com/pdf_f...app_notes/orings.pdf

Could be the type of barrier fluid you are using that is causing the oring to fail, could be the fluid you are pumping is attacking the oring, could be too hot for oring abilities.

The above links have some good images and details of what to look for on oring failures. I understand the DE is the same design, but are you POSITIVE they use the same barrier fluid? 

What you describe above sounds like chemical attack to the oring, if their was problems with mechanical assembly or vibration in nature, this would not cause the oring to do what you describe. Black gunk sounds like dissolved oring material, and out of shape oring also sounds like swelling of the oring material, are you SURE you have viton in both ends and that viton is compatible with your barrier fluid/product

Dave

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